1. Field of the Invention
The present invention relates to electric connectors and more particularly, to an electric power connector in which each male metal terminal comprises a base and two contact prongs bilaterally extended from one side of the base at different elevations, and each female metal terminal comprises a base and two contact prongs forwardly extending from an extension at the base at different elevations and different angles for the contact of the contact prongs of the associating male metal terminal to ensure high stability and reliability in power transmission.
2. Description of the Related Art
When designing an electronic circuit, the circuit designer generally will concern two basic parts, i.e., the part of logic (or signal) and the part of power. Because of the current flowing through a logic circuit is low, the circuit designer needs not to consider the effect of status (for example, temperature) on electrical characteristics (for example, circuit component impedance) when designing a logic circuit. However, the flowing of a high current in a power circuit may cause a significant electric change of the electrical characteristics. Therefore, when designing an electric power connector, the dissipation of heat (due to joule effect) must be taken into account to minimize change of electrical characteristics subject to change of electric current. Further, the contact terminals of an electric power plug generally have the shape of a flat blade or round rod. This is the so-called singular-mass design. In a singular-mass contact terminal configuration, the female metal contact terminal comprises an inwardly projecting pair of suspension arms, and the matching contact blade or prong is set in between the two suspension arms of the female metal contact terminal. This design cannot minimize the size without affecting the heat dissipation efficiency. Further, this design simply allows for adjustment of the geometrical shape of the contact to provide a limited resilience that changes the normal contact force.
Therefore, an improved structure of electric power connector capable changing the normal contact force is developed. According to this design, as shown in FIG. 6, the metal terminal (plug contact) A comprises a base unit having two parallel sidewalls A1, and a front contact unit A2. The front contact unit A2 includes an upper part A21 and a lower part A22. The upper part A21 and the lower part A22 each have a pair of suspension arms. Each suspension arm comprises an inwardly curved proximity portion A211, a remote portion A213, and an arched contact portion A212 connected between the proximity portion A211 and the remote portion A213. The remote portion A213 curves slightly outwards. When the suspension arms are inserted with the front contact unit A2 into a metal contact terminal in an electric socket (not shown) and curved by the contact pressure, the remote portions A213 of each pair of suspension arms forced toward each other to protect against overstress. This double-mass metal terminal design provides a relative greater heat dissipation area when compared to the aforesaid singular-mass metal terminal design. When the plug contact is kept in contact with the matching socket contact, a flow passage is provided around the suspension arms for ventilation of air to dissipate heat. However, this design of metal terminal still has drawbacks. After long and repeated uses, the suspension arms of the upper part A21 and the lower part A22 of the front contact unit A2 may be curved due to elastic fatigue, resulting in contact instability. Further, when one suspension arm is curved or twisted accidentally by an external force, the other suspension arm of the same pair cannot be inserted into positive contact with the socket contact, lowering the electric connection stability and reliability between the plug contact and the socket contact, or resulting in a contact failure.